Formal socio-technical barrier modelling for safety-critical interactive systems design

This paper presents a three step approach to improve safety in the Weld of interactive systems. The approach combines, within a single framework, previous work in the Weld of barrier analysis and modelling, with model based design of interactive systems. The approach Wrst uses the Safety Modelling Language to specify safety barriers which could achieve risk reduction if implemented. The detailed mechanism by which these barriers behave is designed in the subsequent stage, using a Petri nets-based formal description technique called Interactive Cooperative Objects. One of the main characteristics of interactive systems is the fact that the user is deeply involved in the operation of such systems. This paper addresses this issue of user behaviour by modelling tasks and activities using the same notation as for the system side (both barriers and interactive system). The use of a formal modelling technique for the description of these three components makes it possible to compare, analyse and integrate them. The approach and the integration are presented on a mining case study. Two safety barriers are modelled as well as the relevant parts of the interactive system behaviour. Operators’ tasks are also modelled. The paper then shows how the integration of barriers within the system model can prevent previously identiWed hazardous sequences of events from occurring, thus increasing the entire system safety. © 2007 Elsevier Ltd. All rights reserved.